1. Field of the Invention
This invention concerns an improved process for preparing C.sub.1 -C.sub.4 alkanols from synthesis gas with a trimetallic `melt` catalyst. There is an improvement in total C.sub.1 -C.sub.4 alcohol+C.sub.1 -C.sub.4 alkyl acetate productivity, an improvement in C.sub.1 -C.sub.4 alcohol productivity, an improvement in ethanol productivity, and an improvement in total C.sub.1 -C.sub.4 alcohol to C.sub.1 -C.sub.4 alkyl acetates molar ratio.
2. Prior Art
It has long been known that monofunctional alcohols such as methanol, ethanol, etc. can be formed by the reaction of synthesis gas, i.e., a mixture of carbon monoxide and hydrogen at elevated pressures of, for example, up to 1000 atmospheres, and at temperatures of from about 200.degree. to 500.degree. C. or more using as a catalyst a mixture of copper, chromium and zinc oxides. A wide variety of other catalysts have been employed in the reaction of carbon monoxide and hydrogen to yield liquid products containing substantial amounts of monofunctional alcohols as exemplified by methanol, ethanol, propanol, etc.
In U.S. Pat. No. 4,013,700 the reaction of carbon monoxide and hydrogen in the presence of a quaternary phosphonium cation and a rhodium carbonyl complex yields a liquid product having a high methanol content. In U.S. Pat. No. 4,014,913 where the same reactants are contacted with a solid catalyst comprising a combination of rhodium and manganese, the product formed contains substantial amounts of ethanol and in U.S. Pat. No. 4,197,253, where the reaction of carbon monoxide and hydrogen is conducted in the presence of a rhodium carbonyl complex and a phosphine oxide compound, the resulting product contains a high concentration of methanol. Likewise, when the same reactants are contacted with a rhodium carbonyl complex and a copper salt a liquid product containing a substantial amount of methanol is formed.
U.S. Pat. No. 4,332,915 teaches a process of making alkanols, and particularly ethanol, using a catalyst comprising a ruthenium-containing compound and a cobalt-containing compound dispersed in a low melting quaternary phosphonium or ammonium salt.
U.S. Pat. No. 4,332,914 also discloses a process for making alkanols, but with a greater proportion of methanol, using a ruthenium and halogen-free rhenium or manganese compound dispersed in a low melting quaternary salt or base.
A similar catalyst system is used in U.S. Pat. No. 4,362,821, except an inert oxygenated solvent is used. Again, the primary product is methanol.
In cases where bimetallic catalysts are used, it is noted that a ruthenium-containing compound can be used with a second metal comprising nickel or iron, samarium or a Group IVB, VB or VIB containing compound wherein both metals are dispersed in a quaternary phosphonium salt to produce good yields of methanol and ethanol along with some propanol, butanol and esters. See U.S. Pat. Nos. 4,436,837; 4,436,838; and 4,434,248.
None of these references suggests or teaches a trimetallic catalyst which exhibits improved productivity, improved alcohol/ester ratio, improved productivity of total oxygenates, and improved ethyl/methyl ratios.
The discovery of a process exhibiting improved productivity for C.sub.1 -C.sub.4 alcohols plus C.sub.1 -C.sub.4 alkyl acetates using a unique trimetallic catalyst system would be an advance in the art.